1. Section 5-1 What is Genetics?

2. I. What have you inherited? Heredity is the passing of traits from parents to offspring Heredity is the passing of traits from parents to offspring Genes control traits Genes control traits Genes are segments of DNA Genes are segments of DNA

3. A. How are traits inherited? Genes are found on chromosomes in the nucleus of a cell Genes are found on chromosomes in the nucleus of a cell When pairs of genes separate into sex cells during meiosis, pairs of genes also separate from one another When pairs of genes separate into sex cells during meiosis, pairs of genes also separate from one another Each sex cell winds up with one form of a gene for each trait Each sex cell winds up with one form of a gene for each trait

4. Examples of traits that can be inherited: Examples of traits that can be inherited: Eye color Eye color Hair color Hair color Hair line (straight or widow’s peak) Hair line (straight or widow’s peak) One sex cell may receive the trait for straight hair line and another sex cell may receive the trait for a widow’s peak One sex cell may receive the trait for straight hair line and another sex cell may receive the trait for a widow’s peak The different forms a gene may have for a trait are its alleles The different forms a gene may have for a trait are its alleles The study of how traits are inherited is the science of genetics The study of how traits are inherited is the science of genetics

5. II. The Father of Genetics The scientific study of traits pass from one generation to the next was done by Gregor Mendel The scientific study of traits pass from one generation to the next was done by Gregor Mendel Mendel’s background in science and math helped him with his studies of genetics Mendel’s background in science and math helped him with his studies of genetics Mendel studied the inheritance of traits in pea plants Mendel studied the inheritance of traits in pea plants Mendel is known as the “Father of Genetics” Mendel is known as the “Father of Genetics”

6. III. In Mendel’s garden Why did use pea plants in his experiment? Why did use pea plants in his experiment? They are true-breeding – can self-pollinate and produce identical offspring They are true-breeding – can self-pollinate and produce identical offspring They can also be cross-bred – one plant pollinates another to produce a genetic combination in offspring They can also be cross-bred – one plant pollinates another to produce a genetic combination in offspring An organism that always produces the same in its offspring is called a purebred An organism that always produces the same in its offspring is called a purebred Example: A tall plant that always produces a tall plant Example: A tall plant that always produces a tall plant

7. A. Dominant and Recessive Factors Mendel’s first experiment: cross pollinated a purebred of tall plants with a purebred of short plants Mendel’s first experiment: cross pollinated a purebred of tall plants with a purebred of short plants The tall trait is considered a dominant factor because it dominated or covered up the short factor The tall trait is considered a dominant factor because it dominated or covered up the short factor The form of the trait that seemed to disappear is called the recessive. The form of the trait that seemed to disappear is called the recessive.

8. Mendel’s second experiment Self-pollinated the tall offspring and planted the seeds Self-pollinated the tall offspring and planted the seeds The results of this experiment were in a 3:1 ratio. For every 3 tall plants there was 1 short plant. The recessive form reappeared The results of this experiment were in a 3:1 ratio. For every 3 tall plants there was 1 short plant. The recessive form reappeared Genotype: Genotype:

9. B. Predictions Using Probability Probability is a branch of mathematics that helps you predict the chance that something will happen Probability is a branch of mathematics that helps you predict the chance that something will happen What made Mendel’s predictions accurate? What made Mendel’s predictions accurate? He produced a large number of plants He produced a large number of plants By increasing the numbers, Mendel increased his chance of seeing a predicted 3-to-1 ratio By increasing the numbers, Mendel increased his chance of seeing a predicted 3-to-1 ratio

10. IV. Using a Punnett Square A handy tool used to predict results in Mendelian genetics is a Punnett square A handy tool used to predict results in Mendelian genetics is a Punnett square A dominant trait is written with a capital letter and a recessive trait is written with a lower case letter. The letters show the genetic makeup of an organism called the genotype A dominant trait is written with a capital letter and a recessive trait is written with a lower case letter. The letters show the genetic makeup of an organism called the genotype Phenotype refers to the physical appearance of the trait Phenotype refers to the physical appearance of the trait

11. A. Alleles determine traits Most cells in your body have two alleles for every trait Most cells in your body have two alleles for every trait An organism with two alleles for a trait that are exactly the same is called homozygous (TT, tt) An organism with two alleles for a trait that are exactly the same is called homozygous (TT, tt) An organism that has two different alleles for a trait is called heterozygous (Tt) An organism that has two different alleles for a trait is called heterozygous (Tt) The genotype determines an organisms physical traits called the phenotype The genotype determines an organisms physical traits called the phenotype

12. B. Determining genotypes and phenotypes In a Punnett square, the letters representing the two alleles from one parent are written along the top of the square and the alleles from the other parent are written along the side of the square In a Punnett square, the letters representing the two alleles from one parent are written along the top of the square and the alleles from the other parent are written along the side of the square The letters that you filled in each square represent the possible genoytypes for the offspring the parents could produce The letters that you filled in each square represent the possible genoytypes for the offspring the parents could produce

13. C. Mendel’s success Mendel succeeded in describing how inherited traits are transmitted from parent to offspring Mendel succeeded in describing how inherited traits are transmitted from parent to offspring 3 summary statements: 3 summary statements: Traits are controlled by alleles on chromosomes Traits are controlled by alleles on chromosomes An allele’s effect is dominant or recessive An allele’s effect is dominant or recessive When a pair of chromosomes separates during meiosis, the different alleles for a trait move into separate sex cells When a pair of chromosomes separates during meiosis, the different alleles for a trait move into separate sex cells